Russian Journal of Physical Chemistry A最新文献

Atomic force microscopy, scanning electron microscopy, X-ray diffraction phase analysis, voltammetry, and chronopotentiometry are used to study the physicochemical properties of lead coating on steel substrates obtained galvanically. The effect the oxidized surface layer and through pores in the lead coating have on the coating’s function as an anode of chemical power sources is analyzed. It is shown that at positive temperatures, the anodic oxidation of the steel substrate can contribute to the functioning of the anode during a discharge. The high discharge characteristics of lead-coated anodes with no barrier layers on steel substrates at temperatures of −50 to +50°С are confirmed by tests of pilot batches of Pb/HClO₄/PbO₂ reserve power sources. The potential of using tin–lead alloy POS 63 on copper substrates to manufacture anodes for chemical power sources is demonstrated.

We report on simulations of BaFe₁₁TiO₁₉’s magnetocaloric effect (MCE) at temperatures between about 4 and 250 K. The MCE in BaFe₁₁TiO₁₉ unexpectedly displays two forms. Among 33 and 204 K, BaFe₁₁TiO₁₉ shows an inverse MCE due to noncollinear ordering. But when the FM goes from 4 to 33 K or over 204 K, a direct MCE is employed. BaFe₁₁TiO₁₉’s advantages may be useful in the hunt for magnetocaloric compounds that exhibit two or more successive magnetic phase changes. BaFe₁₁TiO₁₉ is therefore a very promising magnet for cryogenic refrigeration, with potential uses in the liquefaction and storage of various gases.

Low-permeability and tight condensate gas reservoirs are critically important in gas field development due to their substantial reserves and high economic value. However, retrograde condensation significantly affects oil and gas productivity during development. Understanding the impacts of interfacial phenomena in porous media is crucial for enhancing recovery rates of gas and condensate oil. This study integrates the capillary effect and adsorption into a phase equilibrium model, based on the Peng–Robinson equation of state (PR-EOS), to account for interfacial phenomena. The results indicate that the interfacial phenomena significantly impact the phase behavior of condensate gas. Interfacial effects increased the dew point pressure (P_d) by 0.47 MPa and the maximum condensate oil saturation (S_omax) by 3.95%. Capillary pressure primarily affects fluid phase behavior and mobility, while adsorption influences fluid composition and interfacial tension. When the capillary radius (r) is less than 100 nm, P_d increases rapidly with decreasing r. At a pore radius of 30 nm, P_d and S_omax increased by 1.06 MPa and 5.23%, respectively. Higher heavy component content in the fluids enhances capillary pressure and desorption, leading to increased P_d and S_omax. Ignoring adsorption and capillary effects can adversely affect reservoir development. The established numerical model considering complex adsorption characteristics and capillary pressure is crucial for understanding phase behavior in high-temperature, high-pressure porous media and optimizing development strategies for condensate gas reservoirs.

Embedded atom model (EAM) potentials are proposed for liquid silicon and germanium. The potentials are calculated from diffraction data using Shommers’ algorithm and presented in the form of tables and piecewise continuous polynomials. Each pair term contributed to the potential takes the form of a hard-sphere model with a downward step. Properties of liquid Si and Ge (density, energy, bulk modulus, and coefficients of self-diffusion) are calculated at temperatures up to 2000 K and agree well with experimental data. It is found that bond directionality virtually disappears after melting at typical densities of liquid Si and Ge. It is suggested that bond directionality might reemerge upon heating and reducing the melt densities by 200–300%.

In this paper, a new simple, and the easy analytical formula is proposed to calculate the second virial coefficient with Yukawa potential. As it is known, the suggested analytical formula can be used to investigate some thermodynamic properties and predictors for protein crystallization and intermolecular interaction potential of fluids. The formula is tested for gas-liquid critical points and Hard-core Yukawa potential with different interaction ranges. The calculation results have been compared with different methods in literature data and the results agree with the literature data. Note that the second virial coefficient can provide significant results in the evaluated protein crystallization and investigate the gas-liquid separation with critical temperature.

Thermodynamic properties of (CaO)_0.501(Al₂O₃)_0.098(SiO₂)_0.401 (Ca40.10) glass are studied using two techniques: low-temperature vacuum adiabatic calorimetry and high-temperature drop solution calorimetry. The enthalpy of formation from oxides (−17.6 ± 2.6 kJ/mol) is determined for the first time. Heat capacity is shown to grow monotonically with temperature in the interval of 8 to 357 K. No phase transitions are revealed in this region of temperatures. Results from measuring heat capacity are approximated using the semi-empirical Planck–Einstein model. The possibility of using incremental scheme to estimate the heat capacity of ternary glasses formed by calcium, aluminium, and silicon oxides is confirmed.

Gibbs energies of the transfer of cryptand[2.2.2] from water to a water–ethanol solvent of variable composition are determined from the interphase distribution of the substance between immiscible phases at a temperature of 298 K composition. It is established that the solvation of cryptand[2.2.2] weakens upon an increase in the concentration of alcohol in the solution. Literature data are used to calculate Gibbs energies of the transfer of protonated cryptand[2.2.2] and complexes of it with nickel(II) and copper(II) ions from water to water–ethanol mixtures.

An experiment is performed on introducing methane with a syringe at different helium flow rates on a chromatographic column free of adsorbent. It is found that the input signals generated in this case are satisfactorily described by an elution curve equation that is a correct solution to the direct problem of linear adsorption dynamics. A separate example shows that the input signals at the same flow rate coincide with one another quite well. The centers of gravity to the left and right of the input signal’s maximum are calculated, considerably expanding its content of information.

Results are presented from studying the permeability of Nafion-type perfluorinated sulfonic cation-exchange membranes used in membrane contact devices (MCDs) for chemical isotopic exchange between water and hydrogen. It is shown that the permeability of a perfluorinated sulfonic cation-exchange membrane grows after modifying it with Fe³⁺ ions and subsequent regeneration with a nitric acid solution. The best effect is observed for Nafion 212 membrane (50.8 µm), since its permeability is approximately tripled in the 298–343 K range of temperatures. It is shown that the state of a membrane has no effect on the observed energy of activation. Energy E_a = 14 ± 4 kJ/mol indicates that isotopic exchange is controlled by diffusion processes.